Broken Vifa D26TG-35

[HAL 8500]

Hello forum members:
I own a pair of 3a Midi Master Gen 2 speakers. These are French “bookshelf speakers” from around 1985.

Unfortunately, one of the two speakers has recently become defective — the tweeter distorts at even moderate volumes and at certain frequencies in the music. I believe it’s likely that the tweeter itself is damaged. Or do you think it’s possible that the crossover is causing the problem? Is there any way I can test this?

The tweeter is labeled “D26TG-35 06 Ω 002,” so it’s a product from Vifa.

Since it seems difficult to buy this exact model of tweeter, I need advice on a suitable replacement. Unfortunately, I’m not sure what the difference is between the installed D26TG-35 and the available D27TG-35 or D26TG-05. Can you give me any guidance on this? Which of the two models is the better replacement, sonically as well as mechanically?

Thanks and best regards,
Hal

 

[knotscott]

It's possible that ferrofluid has either dried up or turned to sludge, and needs to be cleaned out and replaced. The voice coil assemblies are removable/replaceable, and it's a fairly doable DIY project that you can do in an hour or so. Lots of info online.

Madisound or other speaker parts dealers might be able to help if you need a replacement voice coil, or even a suitable tweeter replacement if necessary.

The pics below are for a KEF tweeter, but the process is similar. Remove the tweeter, disassemble the voice coil butterfly from the magnet, clean out old ferrofluid from the voice coil and magnet gap, and replace with new fluid in the magnet gap. Replace the butterfly and reinstall.

 

[bowtie427ss]

Or do you think it’s possible that the crossover is causing the problem? Is there any way I can test this?

Swap the tweeters. If the problem moves with the tweeter to the other speaker, the issue is likely with that tweeter.

If the problem persists on the same side/speaker, there's probably an issue with the x-over or a crusty connection.

 

[Pete B]

I think that the -35 version is chambered for lower resonance, so replace with the same.
I seem to remember reading that the D27 used a newer (better?) dome material but is
nearly drop in for the older one. I believe that you can get just the dome VC from Madisound.
Might want to get two so that they match.

They are due for a recap for NPEs might check if there are film caps in the tweeter section.
But most often distortion is due to a break in the lead in wire or connection. You could
drive the tweeter with a 4.7uF in series outside of the speaker and see if it distorts.

 

[HAL 8500]

Swap the tweeters. If the problem moves with the tweeter to the other speaker, the issue is likely with that tweeter.

If the problem persists on the same side/speaker, there's probably an issue with the x-over or a crusty connection.

That's a great idea. I will try over the weekend.

 

[HAL 8500]

Hello Everyone:
I just want to report back that magically the tweeter repaired itself. I do not understand what happened, but I took the speaker apart mechanically and put it back together, without unsoldering anything though, and now the distortion is gone. I am happy, but puzzled.

Thank you anyway for your suggestions that gave me confidence that I cam take of the problem myself.

Best,
Hal

 

[bowtie427ss]

I took the speaker apart mechanically and put it back together

but puzzled

In a word, oxidation.

Many mechanical connections are prone. It is a product of time + environment.

Working the connections usually exposes bare/clean conductor again, restoring original continuity.

 

[GordonW]

Could be oxidation- could also have been "crap in the gap". Dust or other debris in there, can make for intermittent distortion!

Could be, when it was out of the cabinet, and laying on a table- the debris fell out of between the voice coil and magnet gap.

Regards,
Gordon.